Flesh out Conduit types for Paste search fields

Summary: Ref T9964. This fills in types and descriptions for ApplicationSearch fields in Paste.

Test Plan:
Got this nice table now:

{F1023999}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9964

Differential Revision: https://secure.phabricator.com/D14765

src/applications/spaces/engineextension/PhabricatorSpacesSearchEngineExtension.php

@@ -30,7 +30,9 @@ final class PhabricatorSpacesSearchEngineExtension
         ->setKey('spacePHIDs')
         ->setConduitKey('spaces')
         ->setAliases(array('space', 'spaces'))
-        ->setLabel(pht('Spaces'));
+        ->setLabel(pht('Spaces'))
+        ->setDescription(
+          pht('Search for objects in certain spaces.'));
     }
 
     return $fields;

src/applications/spaces/searchfield/PhabricatorSpacesSearchField.php

@@ -40,4 +40,8 @@ final class PhabricatorSpacesSearchField
     return $phids;
   }
 
+  protected function newConduitParameterType() {
+    return new ConduitPHIDListParameterType();
+  }
+
 }